loading
My son wanted a little telescope.  The optics for this 70mm F/4.3 one were bought on CloudyNights.

The tube is 1/8" thick card-board tubing, impregnated with a mix of Titebond II and water.  The front wider tube holds the lens in place (and there is an inner card-board retainer).  I made the wider tubing by cutting a section of the normal tubing and gluing in a curved segment.

The focuser is a low-profile home-made Crayford-style wooden focuser with PTFE bearing surfaces.  See here.

Unfortunately, only a very light eyepiece works balance-wise in the mount as originally constructed (first photo).  The scope was too small for its Dobsonian-style mount, and moved up and down too easily.  

I modified the mount as in the next photos, by adding a tension adjust on one side.

The third photo shows the right altitude bearing. The nut is superglued in place. If it ever comes unglued, I'll glue something on top of it to keep it in place, or replace it with a threaded insert, or think of something else. The nut actually was a locknut, but I cut out a lot of the locking plastic, so its locking action is very mild.

And the last photo shows the inside of the mount. The black ring is a superglued fiberglass washer. On the other side, under the knob (you can kind of see it in the first photo) there is a superglued washer made from milkjug plastic (rough side facing the wood) so the knob doesn't come undone.
<p>i like this.i bought a 100mm diameter and 20 cm focal length - double convex lens.i would like to know what all other components.and a description of making a 100mm telescope refractor</p>
100mm diameter and 200mm FL will make an F/2 focal ratio. I am afraid that for that kind of a focal ratio, you'd need an extremely high quality apochromatic objective. A double convex lens in that focal ratio will produce distortion that will make the resulting instrument unusable. Sorry!<br><br>What you want is an achromatic objective (you maybe able to buy it used for around $30-50 on cloudynights.com; also, this week SurplusShed has 40% off everything with code SS141014) with about F/5 or slower ratio (diameter to focal length), plus an eyepiece. Then you need to find a way to connect it all.
<p>i like this.i bought a 100mm diameter and 20 cm focal length - double convex lens.i would like to know what all other components.and a description of making a 100mm telescope refractor</p>
<p>i like this.i bought a 100mm diameter and 20 cm focal length - double convex lens.i would like to know what all other components.and a description of making a 100mm telescope refractor</p>
Nice! I liked the simplified Crayford and the idea to cover the tube with Titebond. I'll keep this in mind.

About This Instructable

4,171views

11favorites

License:

More by arpruss:Use 3D printer as a plotter/cutter Finger extensor exerciser 3D printable cookie cutters with Inkscape and OpenSCAD 
Add instructable to: